1. Field of the Invention
The present invention relates to lighting control devices, specifically lighting control devices having linear sliders.
2. Description of the Related Art
Many control devices incorporate linear slide mechanisms on a user interface to allow a continuous range of adjustment of a characteristic of the device being controlled. For example, many residential dimmers include linear sliders for continuous control of the intensity of a connected lamp from a minimum to a maximum value. Also, theatrical stage-boards include many sliders for modification of the intensities, colors, and other characteristics of the theatrical lights during a performance. Finally, many audio electronic devices include linear slides for tuning of the volume of the audio output of the device.
Most prior art slider controls consist of a linear slide potentiometer, a faceplate mounted over the potentiometer, and an actuation member coupled to the potentiometer through a slot in the faceplate for adjusting the linear potentiometer. Typically, the potentiometer is part of a resistive divider and adjustment of the potentiometer will change the output voltage of the resistive divider. The output voltage is provided to a control circuit that will change the characteristic of the controlled device in response to changes in the output voltage of the resistive divider.
Because the location of the slot of prior art slider controls is positioned immediately above the potentiometer, it is common for dirt and dust to build up on the potentiometer. This can cause intermittent behavior of the potentiometer, require periodic cleaning of the slider control, and decrease the lifetime of the potentiometer. Also, since dimmers are connected to line-voltage potentials, the elongated slot in the faceplate can pose a safety issue if a conductive tool, such as a screwdriver, is inserted into the slot and makes contact with the potentiometer and other electrical components of the dimmer.
Some prior art dimmers have included actuation members that provide barrier structures between the slot and the potentiometer. An example of such a dimmer is described in greater detail in commonly-assigned U.S. Pat. No. 6,000,308, issued Dec. 21, 1999, entitled ELECTRICAL SWITCH AND DIMMER CONTROL DEVICE, the entire disclosure of which is hereby incorporated by reference. The actuation member of the dimmer includes a long body portion that extends immediately behind the slot. However, since the body must be situated between the slot and the potentiometer when the adjustment member is positioned at both ends of the slot. Therefore, the body of the actuation member must be substantially twice as long as the length of the elongated slot, which limits the length of the slot. It is desirable to increase the length of the slot as much as possible to enhance the level of intensity control provided by the dimmer.
Thus, there exists a need for a slider control having an increased slot length, wherein the potentiometer is protected from dirt and dust build-up and from tools making contact with the internal electrical components from the outside of the device.